PE barrel onto RM bottom end.

[suzuki27]

I have been thinking about trying a PE250T barrel on my RM250T. The aim is get some more bottom end hopefully. The stock barrel on the RM has had some port work and while it is good on the dirt track it makes it less tractable in MX. I don't mind losing some HP to make it more MX friendly.
I believe it is a straight forward mod. Has anyone tried it or any ideas about doing it- would be appreciated.

[LWC82PE]

It has been proved that there is no difference in the porting. The only difference is the barrel finning/rubbers, so theres not much point in doing what you want to do. Just ask oldfart, he mixed around different RM/PE barrels and couldnt notice a difference.

[huskibul]

 Hey guys sorry to jump in but do you know if its possible to do this with 250-A (pe cylinder) also will a  RM-PE B/C cylinder fit a A bottom end ? much apreciated 

[LWC82PE]

These models share the same base gasket. The TS and DS are center port so would require frame mods and are 70 x 64 and so is the RM250A. If you put a 77-79 PE cylinder (which are side port) on a 76 RM250 your capacity would be 225cc (check port timing/piston heights though)

Part # = 11241-41100
Part Description = GASKET,CYLINDER
Model Count = 13
DS250T 1980 
PE250B 1977
PE250C 1978
PE250N 1979
RM250A 1976 
RM250B 1977
RM250C 1978
RM250C2 1978 1/2
TS250B 1977
TS250C 1978
TS250N 1979 
TS250T 1980
TS250X 1981

[suzuki27]

That's good news. I will put the unmolested PE barrel on the RM.

[suzuki27]

Huskibul, the first PE was designated a B model in 77. No PE- A .The RM250A had a shorter stroke than the following models.
The RM/PE in 77/78(B/C) should be good to swap. See other posts. Cheers.

[huskibul]

  Thanks PE,&27   are the 250 RM'As like the 125 A's in having a completely different barrel/crank/piston arrangement to the RM' B/C,a lot of this stuff is so hard to work out off sites like alpha ,i'am just trying to work out what i can and can't use on a 250-A basket case ive had sitting around (barrel/head missing)without changing the crank which seems fine any info much appreciated  

[LWC82PE]

250 A crank seems to be unique to the model but the rod is common to

Part # = 12161-41100
Part Description = CONNECTING ROD
Model Count = 4
PE250B 1977
RM250A 1976
RM250B 1977
RM250C 1978

It superceeds to

Part # = 12161-41102
Part Description = ROD,CONNECTING
Model Count = 7
PE250B 1977
PE250C 1978
PE250N 1979 
RM250A 1976
RM250B 1977 
RM250C 1978
RM250C2 1978 1/2

That tells me that the rods are the same and the difference is the crank which gives stroke of 64mm instead of 70mm. So i reckon the crank pin is 6mm closer to the edge on the 77-78 model 70mm stroke crank. Thats what the info tells me and i cant think how else they get a different stroke with the same rod.

[Lozza]

I have been thinking about trying a PE250T barrel on my RM250T. The aim is get some more bottom end hopefully. The stock barrel on the RM has had some port work and while it is good on the dirt track it makes it less tractable in MX. I don't mind losing some HP to make it more MX friendly.
I believe it is a straight forward mod. Has anyone tried it or any ideas about doing it- would be appreciated.

That would be a hour to fix, using the same cylinder. Another hour on the dyno will have more low end with the top end restored.

[huskibul]

   While wer'e on the subject of pe barrels fitting rm motors would anybody know if its possible to fit pe175 barrel to rm125-b/c ?cheers

[TM BILL]

   While wer'e on the subject of pe barrels fitting rm motors would anybody know if its possible to fit pe175 barrel to rm125-b/c ?cheers

NO

PE cases at neck are way bigger .

[huskibul]

     Yeah thanks for that bill ,and it could have been so much more fun not that i'am sayin the B isn't heaps'o'fun anyway,no chance of machining down the bottom of the sleeve or another spare set of case's ?  when you say way bigger do you know how much?

[lukeb1961]

Hey guys sorry to jump in but do you know if its possible to do this with 250-A (pe cylinder) also will a  RM-PE B/C cylinder fit a A bottom end ? much apreciated 

We pondered this a year or so back and I was tempted to try. You would end up with a PE270 I think 

[LWC82PE]

You would only end up with 225cc my calculations tell me if you run a 77/78 barrel (67mm) on the 76 bottom end (64mm stroke) i reckon. 67mm bore x 64mm stroke. Im not sure how taller the 77/78 barrel is (if it is taller). If its taller you might be change the crank to the 77 onwards one and have 70 x 70 which will give you 270cc so thats an idea. Or you put the 76 cylinder on the 77/78 cases and that will give you 70x70 aswell (270cc) With 2mm oversize this gets you 285cc and theres probably room in liner to nudge 300cc with a piston sourced from something else. mmmmmmm this gives me ideas Pitty nothing interchanges with T/X/Z though.

[huskibul]

   Ya right there pe&luke,  like the sound of those extra cube's ! if we can just get rid of the if's and but's.would definitly be worth pursuing